1. Field of the Invention
The present invention relates to a positional encoder assembly including a positional encoder and an interface unit releaseably connected with the positional encoder for connecting the positional encoder with a data bus.
2. Description of the Prior Art
Positional encoder assemblies which include a positional encoder, in particular a rotary encoder, which transmits data of operational condition of a drive shaft of a drive unit, via data buses, to an evaluating unit connected downstream of the positional encoder, are known. The positional encoder has a housing, and an interface unit is connected with the housing for connecting the positional encoder with the data bus.
The interface unit is releasably attached to the housing of the positional encoder with screws. The electrical connection between the electronics of the interface unit and the electronics arranged in the housing of the positional encoder is effected by axially pinning the interface unit onto the housing.
The drawback of the known positional encoder assembly consists in that an access to the screws, with which the interface unit is secured to the housing of the positional encoder, is often very difficult after the positional encoder assembly has been mounted on the drive unit. In most cases, the screws can be released with specifically produced screw drivers. Another drawback of the known positional encoder assembly consists in that the electrical connections between the interface unit and the electronics of the positional encoder are hidden in the mounted condition of the interface unit and are, therefore, not accessible and cannot be controlled.
Accordingly, an object of the present invention is a positional encoder assembly having an easily releasable connection of the interface unit with the positional encoder.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing connection means that enable connection and disconnection of the interface unit with and from, respectively, the positional encoder upon displacement of the interface unit relative to the positional encoder.
According to the present invention, the positional encoder assembly includes positional encoder, an interface unit for connecting the positional encoder with a data bus, and connection means which provides for connection of the interface unit with the positional encoder and for disconnection of the interface unit therefrom upon displacement of the interface unit relative to the positional encoder. The interface unit contains adaptive electronics for transmission of the output signals of the positional encoder to the data bus. Preferably, the adaptive electronics includes a memory for storing specific parameters of the positional encoder which can be transmitted back to data bus for an identification of the positional encoder. The connection means for connecting the interface unit with the positional encoder are so formed that the interface unit can be connected with the positional encoder or disconnected therefrom by simply displacing the interface unit in opposite directions.
The advantage of the present invention consists in that the interface unit can be mounted on the positional encoder and dismounted therefrom after the positional encoder has been mounted on the drive unit. A particular advantage of the present invention consists in that the connection of the interface unit with the positional encoder and the disconnection therefrom can be effected with a single movement of the interface unit. A further advantage consists in that no tool is necessary for connecting the interface unit with the positional encoder and its disconnection from the positional encoder.
According to the first embodiment of the present invention, the connection means is so formed that the relative displacement of the interface unit with respect to the positional encoder has a component acting a direction of the positional encoder and a component acting in opposite direction, away from the encoder. In other words, the connection means is so formed that the interface unit moves toward the positional encoder or away from it. Preferable, the interface unit is mounted on the positional encoder or is dismounted therefrom along the positional encoder axis. Alternatively or in addition, the connection and disconnection of the interface unit with or from, respectively, the positional encoder is effected by rotating the interface unit about the longitudinal axis of the positional encoder.
According to an advantageous embodiment of the present invention, the connection means is formed as thread means, e.g., a coarse thread is provided on the outer circumference of the interface unit and cooperates with a corresponding thread provided on the inner circumference of the positional encoder. Such outer and inner threads can be easily formed.
According to a further embodiment of the present invention, the connection means is formed as locking means. Particularly advantageous is when the locking means is formed as a bayonet connection or lock. With such connection means, a particularly simple and reliable connection of the interface unit with the positional encoder is insured. The release of the interface unit is also very easy.
According to present invention, the locking means includes at least one locking lug provided on the positional encoder, and at least one locking opening formed in the interface unit. Alternatively or in addition, a locking lug can be provided on the interface unit, with a corresponding locking opening being formed in the positional encoder. With both embodiments of the locking means, it is contemplated to provide the locking opening with a bevel arranged in such a manner that the locking lug, upon displacement along the bevel during establishing of a connection between the interface unit and the positional encoder, presses the interface unit in a direction of the positional encoder. Alternatively or in addition thereto, the locking opening can be provided with a bevel arranged in such a manner that the locking lug, upon displacement along the bevel, presses the interface unit in a opposite direction, away from the positional encoder.
The bevels substantially facilitate connection of the interface unit with the positional encoder and its disconnection therefrom.
According to a still further embodiment of the present invention, the connection means includes a spring member which can be arranged on the interface unit or the positional encoder and which enables to lock the locking connection, e.g., with such spring member, upon mounting of the interface unit on the positional encoder, the interface unit need be displaced against the baiting force of the spring member, whereby the connection is made more reliable. The spring excursion is used to insure the locking of the locking lug in the locking opening. The spring member is formed preferably as an O-ring arranged in a groove formed on the circumference of the positional encoder.
In accordance with a further advantageous embodiment of the present invention, the connection means includes a sealing which seals the connection between the interface unit and the positional encoder. This embodiment is preferably used where the cooling fluid or the oil can reach the electronics of the positional encoder and destroy it.
In accordance with a still further embodiment of the present invention, the connection means are asymmetrically arranged, with respect to a common axis of the positional encoder and the interface unit, on the positional encoder and the interface unit. Such asymmetrical means insures that the interface unit can occupy only a single predetermined position with respect to the positional encoder. The advantage of the asymmetrical connection means consists in that the electrical and electronic conductors for the positional encoder assembly and the electrical connections within the positional encoder assembly always occupy their predetermined position.
According to yet another embodiment of the present invention, the connection between the positional encoder and the interface unit is secured with appropriate safety means provided in the positional encoder and/or interface unit. Preferably, the safety means is formed as formlockingly engaging means, such as a snap-in connection, e.g., the safety means can be formed as a formlockingly engaging element engageable into the locking bug and/or locking groove, which establish the locking connection between the interface unit and the positional encoder. Such safety means prevents an unintended disconnection of the interface unit from the positional encoder. A member which is formed of a spring steel sheet and is arranged on the positional encoder, proved to be particularly suitable for securing the connection between the interface unit and the positional encoder.
The safety means and the connection means need not be provided in the same location on the positional encoder and/or the interface unit. Rather, the safety means and the connection means can be provided in different locations of the positional encoder and the interface unit.
The interface unit preferably has a plug-in connection means connectable with the electronics of the positional encoder. This is effected advantageously with flexible conductors. Thereby, in distinction from the state of the art, an open and, thus controllable electrical connection between the electronics of the interface unit and the electronics of the positional encoder is insured.
In a particularly preferred embodiment of the positional encoder assembly, as described above, the interface unit is mounted on the positional encoder housing. However, the interface unit can be mounted on any other part of the positional encoder, e.g., on attachment flange.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.